1. Field of the Invention
The present invention relates to a memory refresh system and an operating method thereof, in particular to an embedded dynamic random access memory (eDRAM) refresh system and its operating method.
2. Description of the Related Art
DRAM devices are popular memory devices for storing data in electronic systems. As low power electronic devices are introduced, it is an important subject for DRAM designers to reduce the power consumption. Traditionally, a memory cell of a DRAM includes a transistor and a storage capacitor. The storage capacitor is charged for writing in data. However, after read and write operations have not been executed for a while, a leakage current may result and remove electric charges stored in storage capacitor to cause a data loss, and thus a refresh operation is required to rewrite the data.
Since the leakage current of the storage capacitor is closely related to temperature, therefore the leakage current will rise with temperature rapidly. On the other hand, the leakage current will drop with temperature rapidly. If the operating temperature drops, the memory cell needs not to rewrite the data so frequently. If a refresh frequency is adjusted according to the temperature, then the power consumption of the DRAM will be reduced. In the prior art, a temperature sensor is used for detecting the temperature of the memory, and the temperature sensor can change a self-refresh period according to the detected temperature. For instance, if the temperature sensor detects a lower temperature, the self-refresh period can be maintained for a longer time to reduce the current loss, so as to achieve the effect of power saving.